A folding knife may generally include a lock mechanism to keep the blade of the knife in a locked position when open. This may be helpful to reduce the possibility of the blade accidentally closing on a user's hand during use. For example, U.S. Pat. No. 5,826,340 to Hull discloses a traditional lock mechanism for a folding knife.
The knife includes a lock bar that is pivotally connected to a handle, adjacent the blade. The lock bar includes one lock member, and the blade includes a lock member receiving recess. The lock member includes a bottom wall, and two sidewalls that extend upwardly therefrom. The lock member receiving recess is defined by a bottom wall, and a pair of opposing sidewalls that extend upwardly therefrom. When the blade is in an opened position, the opposing sidewalls of the lock member matingly engage the respective opposing sidewalls of the lock member receiving recess. In other words, when the blade is in the opened position, respective surfaces of the lock member and the lock member receiving recess are in contact with one another.
This type of lock mechanism may, however, be prone to accidental unlocking by the user. Another problem that may occur with this type of lock mechanism is lock failure when a force is applied to a distal portion of the blade.
Another type of folding knife is illustrated in U.S. Pat. No. 5,615,484 to Pittman. This type of folding knife includes a lock mechanism having a stop pin and a slide member that engages the stop pin. When the blade is in the opened position, the stop pin contacts a notch formed in the end of the blade. The stop pin also contacts a sidewall of the slide member when the blade is in the opened position, and the slide member is in an engaged position. To return the blade to the closed position, the slide member is disengaged from contact with the stop pin, allowing the blade to be freely closed. This type of lock mechanism may also be disadvantageous because it may be prone to accidental unlocking by the user.